1. Field of the Invention
The present invention relates to a method of mounting a flat package surface mounting part, such as a large scale integrated circuit (LSI) or an integrated circuit (IC), on a circuit substrate having conductive ink deposited thereon.
2. Description of Related Art
It is known that a surface mounting part such as an LSI or IC can be mounted on a circuit substrate with conductive adhesive. The surface mounting part is electrically connected to lands of the circuit substrate formed by a conductive ink print with conductive adhesive. Conventionally, the shape of the surface mounting part such as a chip diode or chip LED is a guadrilateral with certain intervals between adjacent electrode leads thereof. However, the surface mounting part for an IC for example has at least sixty-four pins to be mounted with the conductive adhesive which is not practical.
Nevertheless, in recent years, surface mounting parts having a plurality of pins have been connected to a circuit substrate by conductive adhesive. However, the conductive adhesive is made of conductive material comprising mainly silver (Ag) to provide a good electric connection and adhesive material to fix the surface mounting part on a conductive ink print circuit substrate. Therefore, the viscosity of the above-mentioned conductive adhesive is less than that of a cream solder for a rigid substrate. To provide sufficient electric property and mechanical property of the conductive adhesive, an emulsion of the conductive adhesive has to be coated in a 0.2-0.3 millimeter thickness. After the conductive ink print circuit substrate is coated with the conductive adhesive, the surface mounting part is mounted on the conductive ink print circuit substrate. The conductive adhesive is then pressed so as to be expanded by electrode leads of the surface mounting part. However, the pressed conductive adhesive on adjacent lands tend to expand and come in contact with each other. Therefore, a circuit pattern must be arranged around the surface mounting part in order to avoid the expanded conductive adhesive. Moreover, the surface mounting part has to be a quadrilateral chip of a comparatively large size and have electrode leads which are sufficiently spaced apart in order to avoid the expanding adhesive on adjacent leads.